1. Field of the Invention
The present invention relates to an illumination light beam forming device in which a plurality of solid light sources are used, an illumination light source device including the illumination light beam forming device and an image display device including the illumination light source device.
2. Description of the Related Art
Conventionally, color illumination technologies emitting illumination light using laser light sources of red, blue and green and forming illumination light of a micro display are known.
In such color illumination technologies, color performance area can be broadened. Also, a light emitting size of the light source is smaller than that of a lamp light source. Therefore, illumination efficiency of the light source is higher than that of the lamp light source. Illumination effects thereof are comparatively brighter in view of power consumption. Consequently, the color illumination technologies using the laser light source can be used with high illumination efficiency towards micro displays. The laser light source is used thereby as the illumination light source of a projector.
In color illumination technologies as such, generally a plurality of laser light sources are disposed two-dimensionally on a substrate and light beams emitted from the plurality of laser light sources are bundled. In addition, in such a color illumination technology, in order to obtain stable light quantity, solid light sources are needed to be efficiently cooled to a desired temperature.
In general, for this cooling, a substrate disposed with a plurality of solid light sources is set onto a holder made of a metal having a comparatively high heat conductivity. In addition, a heat sink or the like with a certain surface area secured thereon is integrated to this holder. Heat generated in the solid light sources is usually absorbed and released by the heat sink thereby such that the solid light sources can achieve stable emission. In additional cases, a cooling fan is employed at times to blow the heat sink for efficient cooling.
However, in the case a double digit number of solid light sources are disposed two-dimensionally (for example, 9 solid light sources are disposed in a 3 line by 3 column matrix), solid light sources arrayed in a peripheral edge portion of the substrate differ in their cooling effects with solid light sources arrayed in a more central side of the substrate.
Specifically, solid light sources at the center are influenced by heat of solid light sources at the peripheral edge portion. Therefore, cooling is not sufficient leading to unstable emitting light or shorter life cycle. Prior art is problematic from these viewpoints. In addition, in order for cooling efficiency to be sufficient, a heat sink large enough than the arrayed area can be disposed in correspondence but downsizing is not possible.
In addition, as disclosed in JP-Hei 11-27472A, attempts are made to increase the arrayed number of solid light sources. JP-Hei 11-27472A discloses an image recording device comprised of a first solid light source group (semiconductor laser group 1) that projects a first plurality of laser beams, a second solid light source group (semiconductor laser group 2) that projects a second plurality of laser beams. In this case of JP-Hei 11-27472A, the first laser beam is transmitted, the second laser beam is reflected. The transmitted first laser beam and the reflected second laser beam are combined by a combining unit.
This combining unit of the image recording device includes a light transmittance member that transmits the first laser beam from one surface side to another surface side. On the another surface side of the light transmittance member, a plurality of small area sized light reflecting mirrors (areas that reflect laser beams by reflection coating) are disposed.
Then the image recording device can include a first light source unit by disposing a first plurality of semiconductor laser elements (semiconductor LED) as the first solid light source group on a first substrate and a second light source unit by disposing a second plurality of semiconductor laser elements (semiconductor LED) as the second solid light source group on a second substrate.
However, the first solid light source group used as transmitting light and the second solid light source group used as reflecting light respectively have light source arrayed two dimensionally. Therefore, for this reason, if high output solid light sources are used as the first and the second solid light source groups, the degree of cooling between solid light sources at the peripheral portion of each light source unit and solid light sources internal to the peripheral portion differs. Thereby the issue of unable to obtain a stable output cannot be cancelled.